Microwave circulator



n /A//// a 1 a E G J T 7 c3 v1 (y 2... xv l z v F H a a 33 u P 24, 1953I c. J. BOSSET ETAL MICROWAVE CIRCULATOR Filed April 25, 1962 INVENTORSCLEBERT J. BOSSET FRANK J. U HES ATTORNEY United States Patent 3,105,206MICRQWAVE (JIRCULATOR Clebert J. Bosset, Newark, and Frank J. Hughes,Anahelm, Calif., assignors to Sylvwia Electric Products Inc acorporation of Delaware Filed Apr. 25, 1962, der. No. 190,105 7 Claims.(Cl. 333--1.1)

This invention relates to improvements in a microwave circulatorconstruction of the type described and claimed in application S.N.59,579, file-d September 39, 1960, entitled Broadband NonreciprocalMicrowave Transmission Device, now Patent No. 3,070,760, and assigned tothe :assignee of this application.

The T circulator described in the above application comprises arectangular wave-guide T with three arms, and a ferrite post or rod inthe junction of the arms and extending transversely of the narrowdimension of the T from one broad wall to the other. In assembling thecirculator, it is necessary to make incremental adjustments of theposition of the post Within the junction to optimize performmice of theci-rculator. Current practice is to secure the post to the :broad wallsof the junction with a Weak adhesive film which can be broken to permitpositioned adjustment, if necessary, and yet is strong enough to holdthe post in place in event no further adjustments are necessary. Itfollows that the adhesive bond is limited in strength thus permittingthe post to loosen under severe vibration or impact.

In accordance with our invention, the post is secured in place by aconstricting force applied through the Walls of the waveguide so as tofrictionally hold the ends of the post. The thickness of the portion ofat least one of the broad Walls of the junction which abuts the ferritepost is reduced so as to be flexible like a diaphragm. One of thepermanent magnets is pressed against the outside of the reduced wall bymeans of a screw to flex the wall inwardly against the end of the postand frictionally lock it in place within the junction. If subsequentadjustments of position of the post are necessary, release of the screwpressure loosens the grip and permits the adjustment and relocating ofthe post.

A general object of this invention is the provision of a simple systemfor releasably locating a ferrite post in a circulator junction withoutthe use of adhesives.

These and other objects of the invention will become apparent from thefollowing description of the preferred embodiment thereof, referencebeing had to the accompanying drawings in which.

FIGURE 1 is a perspective view of a three-port T circulator partiallycut away to illustrate the position of the ferrite post relative to thewalls of the T;

FIGURE 2 is a partial section view taken along line 22 of FIGURE 1illustrating the support arrangement of the post and biasing magnetswithin the T;

FIGURE 3 is a partial section View taken in the dh'ection of line 33 ofFIGURE 1 omitting portions of the arms of the T; and

FIGURE 4 is an enlarged view of a portion of the support arrangementshown in FIGURE 2 illustrating the support of the biasing magnetrelative to the Waveguide wall of the T.

Referring now to the drawings, a preferred embodiment of the inventionis illustrated in FIGURE 1 as a standard H-plane rectangular waveguide T16 comprising three rectangular waveguide arms l1, l2, and 13 having endopenings or ports 14, 15, and 16, respectively, facing outwardly fromjunction 17. At the outer ends of the three arms are mounting flanges18, 19, and 20, respectively, for mechanically connecting the T section19 to associated microwave circuits.

Element 21 which may be gyrom-agnetic material, such as ferrite, in theform of a cylindrical post or rod, is mounted at the junction of thearms ll, 12, and 13 between the top and bottom broad walls 23 and 24,see FIGURE 2, and axially aligned with disc magnets 32 and 33. The rodis located preferably midway between the side walls 29 and 30, seeFIGURE 3, normal to the broad walls and at a distance C from side wall26. Dimension C varies between one-fourth to one-half the longcrosssection dimension A for the optimum location of the post. Theheight of the rod is slightly less than the height dimension B of thewaveguide so that the rod has a slip fit with the inner surfaces of therelaxed broad walls. In order to lock the post between the walls,portions of the broad Walls at the junction are flexed inwardly 'by aconstricting force to frietionally hold the ends of the post in place asexplained hereinafter.

Disc magnets 32 and 33 are located exteriorly of the junction and eachhas a side surface 36 and end surfaces 37 and 37a. These magnets aremounted within substantially identical cylindrical supports 34 and 35 inadditive polarity so that end surfaces 37 and 37a are north and southmagnetic poles, respectively, and produce a constant unidirectionalmagnetic field in rod 21 parallel to its axis 28. In accordance with theprinciple of the circulation as explained in the aforementioned patentapplication, the magnitude of the field is greater than that requiredfor saturation of the ferrite post but is less than that required forferromagnetic resonance, i.e., less than a field which causes precessionof electrons of the ferrite about the axis of magnetic field at afrequency equal to that of the propagating electromagnetic Wave.

Since the upper and lower magnet assemblies are substantially identical,only the upper assembly Will be described in detail below.

Referring now to FIGURES 3 and 4, each of waveguide broad walls 23 and24 is formed with a cylindrical recess 38 in alignment with the centralpart of the junction, and an annular recess 39 at the periphery ofrecess 38. The waveguide wall portion 23a at the bottom of recess 38 issubstantially thinner than the rest of the Wall and therefore is capableof readily being flexed or bowed inwardly of the junction and ofreturning to its original position. The diameter of recess 38 issubstantially larger than that of the ferrite post.

Cylindrical support 34 has an outside diameter substantially the same asor slightly greater than the diameter of annular recess 39 and is pressfitted into and thereafter brazed in the latter with the longitudinalaxis of the sup port normal to broad wall 23. The support is threadedinteriorly throughout its length, minimum diameter of the thread teeth42 being about the same as or slightly greater than the outside diameterof cylindrical magnet 32. The teeth therefore prevent substantiallateral movement of the magnet while permitting it to move axiallywithin the support in the direction of the arrow 47 in FIGURE 4.

A cap 52, see FIGURE 2, threaded into the support abuts the outer end37a of the magnet and is adapted to force the magnet inwardly againstflexible Wall portion 23a. The diameter of the magnet, being less thanthat of recess 38, transmits the axial force of the cap against theportion of the thin wall 23a that is spaced inwardly from peripheralface 44 defining the recess. The thin wall section therefore bowsinwardly, as shown in FIG- URE 4, being hinged to the thicker wallsection at face 44 in the manner of a diaphragm.

A three-port H-plane T-junction circulator with a ferrite post supportarrangement at the junction of the arms and having the followingdimensions and characteristics has been constructed and successfullyoperated:

Waveguide:

Dimension A inches 1.000 Dimension B do 0.400 Dimension C do 0.375Thickness of walls 23 and 24 do 0.050 Thickness of reduced walls 23a do0.025 Rod 21:

Material Magnesium-manganese ferrite. Diameter inch 0.281 Length do0.400 Frequency range gc 8.7-8.8 Isolation:

Minimum db 90 Maximum db 100 insertion loss db 2 VSWR 1.10 Magnets 32and 33:

Diameter inches 0.750 Height do 0.50 Magnetic field intensity gausses600 Supports 34 and 35:

Outside diameter inches 1.0 Inside diameter do 0.750 Thread pitch andseries NEF 20 Recesses 33:

Diameter inches 0.813 Height do 0.025 Caps 52:

Outside diameter -inch Thread series NEF 20 It should be understood thatthis invention in its broadest aspects is not limited to the specificembodiment described above. For example, adequate grippage of the postmay be provided using a single recess 38 adjacent to the ferrite post 21instead of a pair as shown in FIGURE 2. The appended claims are intendedto include all changes and modifications within the spirit and scope ofthe invention.

We claim:

1. A microwave circulator comprising three sections of rectangularwaveguide having broad and narrow walls directly connected in the formof a T-junction with the H-planes of the section parallel, said broadwalls having exterior cylindrical recesses formed therein whereby saidbroad walls are reduced forming thin wall portions at the extremities ofthe recesses,

a ferrite post located within said sections adjacent to said recessesand extending parallel with the narrow Walls thereof,

permanent disc magnets mounted externally of said junction adjacent tosaid post in additive polarity producing a steady magnetic field thereinwith portions of said magnets located within said recesses,

and support means for securing said post relative to said broad wallsand said magnets relative to said post comprising cylindrical supportmembers attached to the broad walls of said sections enclosing saidmagnets and recesses, and having threaded interior surfaces in contactwith said magnets; and cap members having threaded surfaces engageablewith the threads of said support members and end surfaces in contactwith said magnets whereby a constricting force is provided, said forcebeing transmitted through said magnets to said thin wall portions ofsaid broad walls thereby causing elongation thereof to secure said postrelative to said broad walls.

2. A microwave circulator comprising three sections of rectangularwaveguide having broad and narrow walls and directly connected in theform of a T-junction with the H-planes of the section parallel, saidbroad walls having exterior recesses formed therein whereby said broadwalls are reduced at the extremities of the recesses thereby formingreduced wall portions,

a ferrite post located within said sections at said junction adjacent tosaid recesses and extending parallel with the narrow walls thereof,

permanent magnets mounted externally of said junction adjacent to saidpost producing a steady magnetic field therein, said magnets havingportions located within said recesses,

and support means for securing said post relative to said broad wallsand said magnets relative to said post comprising support members incontact with the broad walls of said sections enclosing said magnets,

and means for providing a constricting force to said reduced portions ofsaid broad Walls, said force being transmitted through said magnets tosaid reduced portions thereby causing elongation thereof to secure saidpost relative to the broad walls.

3. A microwave circulator comprising sections of waveguide having 'wallsdirectly connected in the form of a T-junction, said walls havingexterior recesses formed therein,

a ferrite post located within said sections adjacent to said recesses, I

magnets mounted to said Wal is externally of said junction adjacent tosaid post producing a magnetic field therein,

and means for securing said post relative to said broad walls and saidmagnets relative to said post comprising support members in contact withthe walls of said sections and enclosing said magnets, and means forproviding a constricting force to portions of said walls adjacent saidpost, said force being transmitted through said magnets to said portionsthereby causing elongation to secure said post relative said walls.

4. A microwave circulator compnising sections of waveguide having wallsdirectly connected in the form of a T-junction, said walls havingexterior recesses formed therein,

a ferrite post located within said sections adjacent to said recesses,

magnets mounted to said walls externally of said junction adjacent tosaid post producing a magnetic field therein, said magnets havingportions located within said recesses,

and support means for securing said post relative to said broad Wallsand said magnets relative to said post.

5. Support means for a ferrite post within a microwave device comprisinga Waveguide enclosing said post having a longitudinal axis and a recessformed in an exterior surface of said waveguide adjacent to said post,said recess having an axis normal to said waveguide axis,

support members connected to said waveguide adjacent to said post havingvertical axes normal to said waveguide axis, with the axis of one ofsaid members being collinear with said axis of said recess,

first and second magnets located within said support members providing amagnetic field in said post with a portion of said first magnet beinglocated in said recess,

and means for providing a constricting force to a portion of saidwaveguide adjacent to said recess, said force being transmitted throughsaid first magnet to said portion to cause elongation thereof therebysecuring the ends of the post relative to the waveguide.

6. A circulator comprising three rectangular waveguides connectedtogether at a junction with the broad walls of hte wavegiides and of thejunction lying in two parallel planes, respectively,

a ferrite post mounted within said junction normal to said reduced wallportion inwardly of said junction the broad walls thereof and with theends of the whereby said post is compressively frictionally post lightlyengaging the inner surfaces, respectively, gripped by the broad walls ofthe junction, of the junction broad walls, at least one of said juncandmeans for magnetically biasing said ferrite post. tion broad wallshaving the post engaging portion 5 7. The circulator according to claim6 in which said With a reduced Wall thickness whereby said wall lastnamed means comprises at least one permanent magportion may be flexedinwardly and outwardly of net engaging said reduced wall portionexternally of said said junction, junction.

means for releasably applying a flexing force against NO referencesCited-

6. A CIRCULATOR COMPRISING THREE RECTANGULAR WAVEGUIDES CONNECTEDTOGETHER AT A JUNCTION WITH THE BROAD WALLS OF THE WAVEGUIDES AND OF THEJUNCTION LYING IN TWO PARALLEL PLANES, RESPECTIVELY, A FERRITE POSTMOUNTED WITHIN SAID JUNCTION NORMAL TO THE BROAD WALLS THEREOF AND WITHTHE ENDS OF THE POST LIGHTLY ENGAGING THE INNER SURFACES, RESPECTIVELY,OF THE JUNCTION BROAD WALLS, AT LEAST ONE OF SAID JUNCTION BROAD WALLSHAVING THE POST ENGAGING PORTION WITH A REDUCED WALL THICKNESS WHEREBYSAID WALL PORTION MAY BE FLEXED INWARDLY AND OUTWARDLY OF SAID JUNCTION,MEANS FOR RELEASABLY APPLYING A FLEXING FORCE AGAINST SAID REDUCED WALLPORTION INWARDLY OF SAID JUNCTION WHEREBY SAID POST IS COMPRESSIVELYFRICTIONALLY GRIPPED BY THE BROAD WALLS OF THE JUNCTION, AND MEANS FORMAGNETICALLY BIASING SAID FERRITE POST.